[](https://cultofmartians.com/tasks/store-attribute-defaults.html#task)
[](https://rubygems.org/gems/store_attribute)
## Store Attribute
ActiveRecord extension which adds typecasting to store accessors.
Originally extracted from not merged PR to Rails: [rails/rails#18942](https://github.com/rails/rails/pull/18942).
### Install
In your Gemfile:
```ruby
# for Rails 6.1+ (7 is supported)
gem "store_attribute", "~> 1.0"
# for Rails 5+ (6 is supported)
gem "store_attribute", "~> 0.8.0"
# for Rails 4.2
gem "store_attribute", "~> 0.4.0"
```
### Usage
You can use `store_attribute` method to add additional accessors with a type to an existing store on a model.
```ruby
store_attribute(store_name, name, type, options)
```
Where:
- `store_name` The name of the store.
- `name` The name of the accessor to the store.
- `type` A symbol such as `:string` or `:integer`, or a type object to be used for the accessor.
- `options` (optional) A hash of cast type options such as `precision`, `limit`, `scale`, `default`. Regular `store_accessor` options, such as `prefix`, `suffix` are also supported.
Type casting occurs every time you write data through accessor or update store itself
and when object is loaded from database.
Note that if you update store explicitly then value isn't type casted.
Examples:
```ruby
class MegaUser < User
store_attribute :settings, :ratio, :integer, limit: 1
store_attribute :settings, :login_at, :datetime
store_attribute :settings, :active, :boolean
store_attribute :settings, :color, :string, default: "red"
store_attribute :settings, :colors, :json, default: ["red", "blue"]
store_attribute :settings, :data, :datetime, default: -> { Time.now }
end
u = MegaUser.new(active: false, login_at: "2015-01-01 00:01", ratio: "63.4608")
u.login_at.is_a?(DateTime) # => true
u.login_at = DateTime.new(2015, 1, 1, 11, 0, 0)
u.ratio # => 63
u.active # => false
# Default value is set
u.color # => red
# Default array is set
u.colors # => ["red", "blue"]
# A dynamic default can also be provided
u.data # => Current time
# And we also have a predicate method
u.active? # => false
u.reload
# After loading record from db store contains casted data
u.settings["login_at"] == DateTime.new(2015, 1, 1, 11, 0, 0) # => true
# If you update store explicitly then the value returned
# by accessor isn't type casted
u.settings["ratio"] = "3.141592653"
u.ratio # => "3.141592653"
# On the other hand, writing through accessor set correct data within store
u.ratio = "3.141592653"
u.ratio # => 3
u.settings["ratio"] # => 3
```
You can also specify type using usual `store_accessor` method:
```ruby
class SuperUser < User
store_accessor :settings, :privileges, login_at: :datetime
end
```
Or through `store`:
```ruby
class User < ActiveRecord::Base
store :settings, accessors: [:color, :homepage, login_at: :datetime], coder: JSON
end
```
### Using defaults
With `store_attribute`, you can provide default values for the store attribute. This functionality follows Rails behaviour for `attribute ..., default: ...` (and is backed by Attribute API).
You must remember two things when using defaults:
- A default value is only populated if no value for the **store** attribute was set, i.e., only when creating a new record.
- Default values persist as soon as you save the record.
The examples below demonstrate these caveats:
```ruby
# Database schema
create_table("users") do |t|
t.string :name
t.jsonb :extra
end
class RawUser < ActiveRecord::Base
self.table_name = "users"
end
class User < ActiveRecord::Base
attribute :name, :string, default: "Joe"
store_attribute :extra, :expired_at, :date, default: -> { 2.days.from_now }
end
Date.current #=> 2022-03-17
user = User.new
user.name #=> "Joe"
user.expired_at #=> 2022-03-19
user.save!
raw_user = RawUser.find(user.id)
raw_user.name #=> "Joe"
raw_user.expired_at #=> 2022-03-19
another_raw_user = RawUser.create!
another_user = User.find(another_raw_user.id)
another_user.name #=> nil
another_user.expired_at #=> nil
```
It is possible to configure `store_attribute` to return the default value even when the record is persisted and the attribute name is not present. By using the `store_attribute_unset_values_fallback_to_default` class option, default values will be returned for missing keys. For example:
```ruby
class User < ApplicationRecord
self.store_attribute_unset_values_fallback_to_default = true
end
user = User.create!(extra: {})
user.expired_at #=> 2022-03-19
```
**IMPORTANT:** Due to implementation limitations, it's not recommended to toggle the value of `store_attribute_unset_values_fallback_to_default` in sub-classes. We recommend to set this value in base classes (e.g., `ApplicationRecord`).